This invention concerns improvements in or relating to laser drilling of components.
The performance of a gas turbine engine depends in part on its operating temperature. The quest for improved aircraft gas turbine engine performance now results in very high temperature gas streams within the engine. Gas stream temperatures may exceed the melting point of a component such as a turbine blade working within the gas stream.
Clearly, the component must be kept as cool as possible, and one way of achieving this is to provide a flow of cooling air over the surface of the component through holes in the surface communicating with a cold air supply within the component.
The shape, size and disposition of the cooling holes are of paramount importance for efficient cooling, and one way of providing holes of required accuracy is by laser drilling.
Laser drilling of a metal alloy turbine blade is done by directing through a nozzle at the blade a laser beam focused through a lens assembly, together with a high pressure oxygen supply. It is important that the distance between the nozzle and the surface of the blade is kept constant, otherwise the focusing of the laser beam on the blade will be adversely affected and the quality of thehole being drilled will suffer.
It is an object of the present invention to provide a method of maintaining constant the distance between the laser nozzle and the surface of the component being drilled over a region of the surface.